1. Field of the Invention
The present invention concerns an apparatus for the magnetic induction heating of rectangular, flat metal products traveling along their longitudinal axis. The apparatus is of a type comprising at least one inductor capable of producing a controllable magnetic field of constant intensity, oriented essentially perpendicularly to a wide face of the metal product to be heated. The inductor is mounted so as to rotate about an axis perpendicular to the wide face of the metal product and comprises at least two magnetic poles having polar surfaces facing the wide face and parallel to it. The magnetic poles sweep an annular area as the inductor rotates about the axis perpendicular to the wide face of the metal product.
The use of rotating inductors to generate a magnetic field of constant but controlled intensity to heat metal products to be hot worked has been known for a long period to time (see for example French Pat. Nos. 916,287 and 1,387,635). The magnetic poles may consist of permanent magnets, electromagnets or a combination of permanent and electromagnets. The inductor or inductors may be placed externally about a refractory tunnel of a material permeable by the magnetic field through which the metal products to be heated are passing.
The known devices for induction heating have seldom been previously used for the reheating of metal products, such as slabs or blooms, i.e. when the slabs have already undergone several passes through the roughing stands of a rolling mill, but not the finishing stands of the mill. In addition, experience has shown that it is difficult to obtain a regular temperature profile in the transverse direction of the metal products to be reheated with the previously known heating devices. This problem becomes even more complex in view of the fact that the metal products to be heated may have widths varying over a wide range of values.